1. Field of the Invention
This invention pertains to the field of 2-haloacetanilides and their use in the agronomic arts, e.g., as herbicides, particularly for use in transplant rice.
2. Description of the Prior Art
The invention compounds are characterized as 2-chloroacetanilides having an n-butoxy radical in one ortho position, an ethyl radical in the other position, and as a substituent on the anilide nitrogen ring a C.sub.1-5 alkyl radical, perferably methyl or ethyl.
The prior art relevant to this invention includes numerous disclosures of 2-haloacetanilides which may be unsubstituted or substituted with a wide variety of substituents on the anilide nitrogen atom and/or on the anilide ring including alkyl, alkenyl, alkynyl, alkoxy, polyalkoxy, alkoxyalkyl, heterocyclyl, halogen, etc., radicals. The most relevant compounds of the prior art in this area appear to be those disclosed in the following references: U.S. Pat. Nos. 3,268,584, 3,442,945, 3,773,492 and 4,152,137. However, none of those prior art references disclose any data for compounds of the type disclosed herein as being useful transplant rice herbicides, nor do they disclose or suggest the particular species of this invention.
The 2-haloacetanilides of the prior art which are known to have utility as transplant rice herbicides differ significantly in structure from those disclosed herein. Specifically, said prior art herbicides all contain lower alkyl radicals in both ortho positions to the anilide nitrogen atom and an alkoxyalkyl radical on said nitrogen atom. Accordingly, those prior art rice herbicides are non-related and non-suggestive of those disclosed herein. However, in order to provide a basis for comparison, the relative herbicidal efficacy of preferred compound of this invention is compared with that of relevant prior art herbicides; data are presented in tables herein.
The above-mentioned 2-haloacetanilides of the prior art are MACHETE.RTM. (registered trademark of Monsanto Company), the active ingredient of which is 2',6'-diethyl-N-(n-butoxymethyl)-2-chloroacetanilide (common name "butachlor"); 2',6'-diethyl-N-(n-butoxyethyl)-2-chloroacetanilide ("ethyl butachlor" herein); 2-tert-butyl-6-methyl-N-(n-butoxymethyl)-2-chloroacetanilide (common name "terbuchlor"), and 2',6'-diethyl-N-(2-propoxyethyl)-2-chloroacetanilide (common name "pretalachlor"). Butachlor and ethyl butachlor are disclosed as rice herbicides in U.S. Pat. No. 3,663,200; terbuchlor is disclosed as a transplant rice herbicide in U.S. Pat. No. 3,955,959 and pretalachlor is disclosed as a rice herbicide in U.S. Pat. No. 4,168,965. Of the foregoing herbicides, only MACHETE herbicide has achieved commercial status.
While the above rice herbicides have been found useful, there is a continuing need for improved rice herbicides which control resistant weeds of economical significance at lower rates of application, maintain control or suppression of such weeds for longer periods of time, while maintaining safety to the rice crop and improved toxicity with respect to fish and mammals.
The above prior art herbicides have been found to share one or more undesirable properties as transplant rice herbicides. Among certain disadvantages of those prior art herbicides are: (1) their generally weak performance in the control and/or suppression of the economically-significant resistant perennial weeds Eleocharis kuroguwai and Sagittaria trifolia and (2) diminishing efficacy in the control or suppression of the perennial weed Cyperus serotinus and the annual weeds Echinochloa crus-galli and, to a lesser extent, Monochoria vaginalis, within a period from 2-6 weeks.
These performance weaknesses are particularly apparent at lower rates of application, i.e. down to 0.17 lb/A (0.19 kg/ha) and lower. In fact, field tests have shown that in some treatments some of the prior art herbicides failed to selectively control Eleocharis kuroguwai at rates below 2.67 lb/A (3 kg/ha) or even up to 5.36 lb/A (6 kg/ha), or higher, for periods as short as 2 or 3 weeks. Similarly, in field tests, it was also found that some of the above prior art rice herbicides failed to provide any meaningful suppression of Sagittaria trifolia after four or five weeks.
It is, therefore, an object of this invention to provide a class of herbicides which are particularly useful in transplant rice.
A further object of this invention is the provision of selected herbicides which: (1) are safe (i.e., produce no more than about 15% injury) on transplant rice at rates up to at least 5.0 lb/A (5.60 kg/ha); (2) selectively control Echinochloa crus-galli, Monochoria vaginalis and Cyperus serotinus at rates below 0.35 kg/ha (0.34 lb/A) for up to at least seven weeks; (3) selectively control Eleocharis kuroguwai at rates as low as 3.0 kg/ha (2.67 lb/A) for as long as five weeks and (4) provide increased suppression of Sagittari trifolia for up to seven weeks.
It is a further object of this invention to provide a transplant rice herbicide having improved fish toxicity relative to the above prior art herbicides.
Finally, it is an advantage of the herbicides of this invention that they are safe and require no special handling procedures.
The above and other objects of the invention will become more apparent from the detailed description below.